John often lay awake at night wondering what he would do if anything happened to Sherlock. He suspected everyone would think he was fine if he was suddenly on his own. He was John Watson. John Watson was a tough guy, the ex army man. The guy you wanted on your side in a fight. The guy who had seen it all and come out the other side laughing. But John knew the truth of it.
Death was easy.
Falling into the accepting arms of death was easy. What was hard was being sent back to the living after you died with a chunk gouged out of your soul. What was hard was having no way of knowing whether you were alive or not. What was hard was not having Sherlock.
Sherlock lay awake wondering what he would do if John died. Before John, Sherlock had never considered he was lonely, the same way a blind child does not know it is blind until someone tells it. But Sherlock knew now what had been missing from his life. Which giant chunk of his being had been gouged out by unseen hands and left him without. Dying Sherlock had no worries about. Being without John bothered him greatly.
Sherlock was certain that John would be okay without him. After all John was normal. John had friends and emotions and John cared about things and cried at the end of films. So John would be fine.
John was sure Sherlock would be okay if anything happened to him. Sherlock didn't really need anyone. If John was being realistic he was just an interesting diversion and one day Sherlock would get bored with him. John knew that. He wasn't stupid. And if John died, well Sherlock would be fine.
Secretly Sherlock had a plan. If anything happened to John he had already selected the quickest acting poison he could find. It would be easy.
Secretly John had a plan. If anything happened to Sherlock he had his revolver ready and waiting. He'd been shot before. It would be easy.
Death for Sherlock and John would just be the next awfully big adventure. But although neither would admit it, it was an adventure neither was prepared to let the other face alone.